It is well recognized that macrophage-mediated inflammation plays a key role in vascular pathophysiology, including that leading to atherosclerosis and angiogenesis. Integrin adhesion receptors are critically involved in monocyte/macrophage recruitment, localization, differentiation, and effector function. Based on the preliminary data in our laboratory that leukocyte (T lymphocyte) [unreadable]2 integrin engagement leads to activation of the Rho family GTPase Rac-2, and that this activation results in modulation of gene expression, this proposal is focused on identifying Rac-2 targets in macrophages and on determining the importance of Rac-2 in vascular pathology models. The hypothesis is that Rac-2, through effects on gene expression and/or protein phosphorylation, is a critical mediator of those vascular pathology (or physiology) states requiring macrophage localization and activation, such as atherosclerosis and inflammatory angiogenesis. The specific aims of this 3 year project are to: 1. Demonstrate that leukocyte integrin engagement results in Rac-2 and Rac-2 effector activation in murine macrophages, using Rac-GTP pull-down assays and phospho-MAP kinase immunoblots;2. Identify proteins whose levels and/or phosphorylation status are increased in murine macrophages transfected with a construct expressing a constitutively active Rac-2 (Q61L), using proteomic and phosphoproteomic analyses, with bioinformatic efforts to identify novel Rac-2 targets;and 3. Document a role for Rac-2 in vascular pathology and physiology, using Rac-2 gene-deleted mice in atherosclerosis (ApoE-/-) and hindlimb ischemia models. The long term objective of the proposed work is defining macrophage-specific inflammatory biomarkers and/or molecular imaging targets in vascular pathology, including acute and chronic atherosclerotic syndromes, as well as angiogenesis. My goal is to utilize this project and these findings as the foundation for my physician-scientist career. The immune system, which includes inflammation, is critical to defense against infections. It also plays a role in altering blood vessel health, leading to coronary artery disease and to new vessel formation when blood supply is lacking. This work will define inflammation proteins, expressed in immune cells that could serve as markers of progressive, vascular disease, and as imaging or therapeutic targets.